Hyperprolactinaemia in patients with pituitary adenomas. The pituitary stalk compression syndrome.

Hyperprolactinaemia, unexplained by prolactin-production of the tumour is occasionally found in patients with pituitary tumours. This secondary hyperprolactinaemia has been ascribed to a mass effect of the tumour upon the pituitary stalk, obstructing the normal inhibitory hypothalamic influence on the prolactin producing cells. In this study the adenoma volume, amount of suprasellar enlargement of the tumour and the intrasellar pressure were measured in 42 patients operated upon consecutively for pituitary tumours. Secondary hyperprolactinaemia was found in six (14%). There was no difference as regards adenoma volume, amount of suprasellar extension or intrasellar pressure between the group of patients with elevated p-prolactin versus the group with normal p-prolactin. We conclude that mechanisms other than pituitary stalk compression must be considered as the cause of secondary hyperprolactinaemia.